Interconnect for implantable medical device header

ABSTRACT

A modular header and method of fabricating same for making electrical connection between an array of feed-through pins extending through a wall of a hermetically sealed enclosure of an implantable medical device and lead connect or receptacles within the header in which the header is fabricated using a pre-formed molded header module, together with a set or harness of interconnected flexible conductors incorporated and sealed by an overlayer of medical grade polymer material. The assembled modular header is capable of complete pre-testing prior to assembly onto an implantable medical device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/860,364 entitled “INTERCONNECT FOR IMPLANTABLE MEDICALDEVICE HEADER,” filed on Sep. 24, 2007, which is a continuation of U.S.patent application Ser. No. 10/320,044, now issued as U.S. Pat. No.7,274,963, entitled “INTERCONNECT FOR IMPLANTABLE MEDICAL DEVICEHEADER,” filed on Dec. 16, 2002 by Spadgenske and assigned to CardiacPacemakers, Inc., the disclosure of each of which is incorporated hereinby reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to implantable medical deviceshaving external electrical connections and electrical feed-throughs and,more particularly, to the provision of a pre-built modular sub-assemblyinterconnect system for a header module such as are found in implantablepulse generators (IPG's) associated with cardiac rhythm management andother hermetically sealed implantable medical devices.

II. Related Art

Implantable medical devices of a class having electrical circuitcomponents are well known in the medical field. These include cardiacrhythm management devices which commonly include a pacemaker unit which,in turn, includes sensing and control circuitry, together with a powersupply, protectively housed in a hermetically sealed case or can incombination with one or more conductive electrical leads designed toconnect to the patient's heart muscle tissue, the activity of which isto be sensed and stimulated. To maintain the integrity of the componentsin the sealed case, provision must be made for hermetically sealedpassage of electrical conductors to the exterior for connection to theleads and ultimately to tissue of interest. This has been typicallyaccomplished by using connector blocks and associated feed-throughconductors located external to the IPG housing which, themselves, aretypically placed within a sealed header structure of medical gradepolymer material.

While great strides have been made in improving the sophistication ofthe pacemaker devices themselves, the assembly and testing of thedevices has remained relatively dependent on the skill of the assemblyworkers. Attempts have been made in the art to simplify the assemblyprocess and to improve the acceptance rate of completed devices whichundergo rigorous testing once assembled. In U.S. Pat. No. 5,282,841, forexample, a ribbon conductor set or harness is provided to facilitateconnection of feed-through terminal conductors to correspondingconnector blocks in the header in which the individual ribbon conductorsleads can be shaped to a three-dimensional geometry for ease ofassembly. The assembled or fully interconnected unit is thereaftersubjected to an over molding or coating step in which an entire epoxyhead is cast over the assembly to encapsulate and seal the connectingcomponents. That system, however, still depends on the skill of workersfor assembly and requires extensive over molding. Furthermore, theelectrical integrity of the unit cannot be tested until it is completelyassembled.

U.S. Pat. No. 6,205,358 B1 discloses a pre-formed header module incombination with a ribbon connector harness which is assembled andplaced between feed-through pins on the side of the sealed enclosure andthe header module and thereafter captured in an over molding orbackfilling step using medical grade polymer. This system also suffersfrom similar drawbacks to those described above.

SUMMARY OF THE INVENTION

By means of the present invention there is provided a module headersub-assembly for assembly to in connection with a hermetically sealedimplantable medical device which solves many of the above problems andovercomes the drawbacks of previous versions of such devices. Thepresent invention provides the desired electrical feed-through, but,unlike previous header units, the header of the present invention is asufficiently complete sub-assembly such that it can be tested forfunctional integrity prior to assembly onto the hermetically sealedmedical device. The present header also facilitates assembly and reducesthe amount of necessary backfill.

The modular header sub-assembly of the present invention eliminates therouting of individual feed-through wires to the respective connectorblocks by providing an array of metallic conductors incorporated intothe sub-assembly itself and molding in either the primary, secondary oreven a tertiary mold operation. In this manner, one end of each of theflexed conductors is connected to the appropriate connector block andthe other end aligned with the remaining traces to be connected tocorresponding feed-through pins in the hermetically sealed IPG unit. Inthis manner, an array of aligned connectors is arranged to match anarray of aligned feed-through pins such that connection between them canbe made through a small window readily backfilled after connecting andwelding operations. This enables additional site connectors to beimplemented while maintaining and actually decreasing header size whencompared to conventional wire routings. The flex or trace design furtherallows all weld locations to be in a minimal number of weld accessplanes and therefore readily adaptable to process automation.Furthermore, pre-fabricated wire terminations provide repeatableattached locations on conductor sites making feasible alternate weldingtechniques such as programmable micro-laser welding.

The reduction of the volume required to be backfilled after weldingoperations also eliminates concerns with respect to the sealingintegrity of the backfill which is currently dependent on the techniqueand skill of the operator and the subsequent inspection. Thepre-fabricated wire terminations further eliminates a majormanufacturing step involved in routing and backfilling of the wirechannels in the header and further allows testing of the integrity ofeach conductor in the header prior to assembly of the header to thehermetically sealed device. Since the flex/conductor system can be anintegral part of the header, mold/sealing operations requiring highpressures are now possible since the header does not have to beconnected to the device prior to these primary or secondary mold/sealoperations.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic representation of an implantable medical device inthe form of an IPG of a class suitable for including the headerinterconnect system of the present invention;

FIG. 2 is a greatly enlarged perspective view of a primary molding of apre-formed header module showing pre-formed patterned conductor channelsand including connector blocks adapted to receive a correspondingconnected array system or harness of flexible connectors in accordancewith the present invention;

FIG. 3 is a perspective view similar to that of FIG. 2 as it is beingaddressed and fitted with a pre-formed harness of flexible conductors inaccordance with the invention;

FIG. 4 depicts the pre-formed header module of FIGS. 2 and 3 with theconnector system assembled in place;

FIG. 5A is a view of the pre-formed header module of FIG. 4 after theapplication of a secondary overlayer of medical grade polymer;

FIG. 5B is a view similar to FIG. 5A with the header module rotated tobetter depict the array of connecting terminals adapted to receive thefeed-through pins of a corresponding hermetically sealed device;

FIGS. 6-8 depict views of assembly steps characteristic of analternative embodiment of an inline connector design using a sideconnection system in the modular header; and

FIG. 9 shows an assembled device with parts cut away exposing theconnection and greatly enlarged fragment views of a typical connectionmode in accordance with the assembly of the header of the invention ontothe hermetically sealed implantable unit.

DETAILED DESCRIPTION

It will be appreciated that the present invention enables the header tobe built as a complete modular sub-assembly capable of being tested forcircuit integrity prior to attachment to the feed-through pins of thehermetically sealed pacer, other IPG or other implanted unit. Thepresent invention also greatly simplifies the connection process andreduces the amount of backfilling required to complete theheader/hermetically sealed IPG assembly. While the detailed descriptionwhich follows is limited to one or two embodiments, it will also beunderstood that these are intended as examples only and are not intendedto limit the scope of the inventive concept in any manner.

FIG. 1 depicts a simplified schematic view of an implantable medicaldevice 20 of a class suitable for utilizing the header of the presentinvention including a pre-formed, pre-assembled header module 22attached to a hermetically sealed enclosure 24. A plurality of leads 26,which typically includes atrial and ventricle pacing/sensing leads, forexample, are connected to the header using elongated lead connectors 28and receptacles as at 30. The leads are further connected tofeed-throughs using feed-through pins extending through the hermeticallysealed enclosure 24. These are beneath the backfilled surface and so arenot shown in the figure.

Generally, the hermetically sealed enclosure 24 contains a power sourcein the form of an electrochemical cell which may be a lithium battery,control and sensing circuitry which controls the operation of the deviceand senses and records data according to programmed instructions whichmay be fixed or time-variable and microprocessor controlled. A telemetrytransceiver system is provided to enable the device to communicate withan external programmer.

It will be appreciated that particular electronic features may varyconsiderably from device to device and the practice of the presentinvention is not dependent or based on any particular embodiment of sucha unit, but is based on a common need for pass-through connections.

FIG. 2 is a greatly enlarged perspective view of a pre-formed moldedheader module 40 having a plurality of elongated external lead connectorreceptacles as at 42. The pre-formed primary header module is providedwith a plurality of recessed conductor channels as at 44 and 46 whichconnect with corresponding connector blocks as at 48 and 50. The leadconnector receptacles 42 also connect with corresponding connectorblocks 48 and 50 through internal passages (not shown) in a well knownmanner.

As shown in FIG. 3, the pre-formed flex conductor system or harness 51is provided with leads or conductors represented by even referencecharacters 52 through 66 configured to fit into the correspondingrecessed channels 44, 46 and to have corresponding free ends designed toattach to corresponding connector block as at 48 or 50, or otherwise(not shown) each flexible connector further having a second end fixed inspaced relation along a removable common member 68 provided forproduction of the harness and ease of assembly onto the primary moldedmodule 40.

FIG. 4 depicts the molded module 40 of FIGS. 2 and 3 with the flexibleconductors, which may be constructed of a conducting foil, or the like,situated in place in the corresponding relevant receiving channels 44,46. The material of the flexible conductors 52-66 is one easily deformedto fit the relevant recessed channel 44, 46 yet is sufficiently ruggedto withstand the manufacture, assembly and a subsequent over-moldingoperation while remaining intact. The material conductive of the tracesor harness is preferably a stainless steel, but other bio-compatiblematerials which adapt themselves to the manufacturing and assembly stepssatisfactorily in accordance with the invention may be used.

FIGS. 5A and 5B illustrate the pre-molded or primary molded headermodules 40 of FIGS. 2-4 after application and routing of the conductivetraces in the channels 44, 46 and connection of them to thecorresponding connector blocks, some of which are illustrated at 48 and50, and after a secondary molding or first over-molding step has beenperformed and the common member 68 has been removed. The over-moldinglayer 70 seals the conductors within the modular header exposing onlythe external connection sites as at 42, 48 and 50 and an array ofterminal spade connectors 72 adapted to be connected to correspondingfeed-through pin 74 shown in FIG. 9. As shown particularly in theenlarged fragment views of FIG. 9, the spade connectors 72 can readilyand automatically be crimped about feed-through pins 74 and theconnection welded as at 76.

FIGS. 6-8 depict an alternative embodiment utilizing an inline externalconnector configuration including a pre-molded header module 80 havingan array of inline external connection openings as at 82 adapted toreceive external leads (not shown) in the usual well known manner. Anarray of possible side co-planar terminals or block connection sites asat 84 are provided and these are addressed by a pre-formed flexconductor system or harness 86 containing an array of leads or traces asat 88 not unlike those previously discussed and connected formanufacturing and assembly purposes by one or more stabilizing membersas at 90, as shown in FIG. 7. In FIG. 7, the free ends of the traces 88are shown in place on the side of module 80 and connected to the sites84. Here, as in the case of the embodiment earlier described, connectionis readily achieved by an assembler. These traces also are provided withspade connectors 72.

FIG. 8 depicts the modular header 80 after the application of anoverlayer 92 of medical grade polymer on the connection side which sealsin the conductors 88 leaving only the array of terminal spade connectors72 conveniently configured in an inline arrangement correspondingfeed-through terminal pins 74 as depicted in FIG. 9 in the mannerpreviously described.

Note that the remaining recess volume 75 in FIGS. 5A and 5B and 94 inFIG. 8 is quite small in relation to the size of the header module 40 or80, such that the amount of backfilling after final connection to fillout and streamline the structure remains relatively minor.

The embodiments, once assembled, can easily be tested as by plugging theheader module into a test stand and attaching any desired externalleads. The use of the harness in combination with predetermined separatepaths for the conductors precludes shorts and eliminates the need forusing insulated conductors.

This invention has been described herein in considerable detail in orderto comply with the patent statutes and to provide those skilled in theart with the information needed to apply the novel principles and toconstruct and use such specialized components as are required. However,it is to be understood that the invention can be carried out byspecifically different equipment and devices, and that variousmodifications, both as to the equipment and operating procedures, can beaccomplished without departing from the scope of the invention itself.

What is claimed is:
 1. A method of fabricating a modular header forproviding electrical connections between an array of feed-through pinsextending through a wall of a hermetically sealed enclosure of animplantable medical device and lead connector receptacles within amodular header assembled to said device comprising: (a) providing apre-formed molded header module having paths therein to accept andincorporate a set of flexible conductive traces and connector blocks;(b) providing a set of interconnected flexible conductors each having afree end and a fixed end, and assembling said set of conductors intosaid recesses by said pre-formed molded header module attaching the freeends thereof to corresponding connector blocks provided in said moldedheader module; (c) performing an over-molding operation to incorporateand hermetically seal said conductors into said header structure.